<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    span{
      display: inline-block;
      /* width:50px;
      height:50px; */
      /* background-color:blue; */
      /* border-radius: 50%; */
        
      border-top:50px solid red;
      border-right:50px solid yellow;
      border-bottom:50px solid green;
      border-left:50px solid pink;
    }
  
  </style>
</head>
<body>
  
  <span></span>
</body>
</html>